Photonic elements include a light emitting diode (LED) configured to emit light upon application of an electric current, and a photoelectric conversion element configured to generate an electromotive force upon application of light. Such a photonic element is typically encapsulated by an encapsulant.
An epoxy resin having high adhesive properties and excellent dynamic durability has been widely used as an LED encapsulant (for example, Patent Documents 1 to 3). However, the epoxy resin has problems in that it has low transmittance with respect to light ranging from blue to ultraviolet (UV) wavelength ranges, and also shows lower light resistance.
Also, an ethylene vinyl acetate (EVA) material has often been used as an encapsulant configured to encapsulate the photoelectric conversion element. However, the EVA material has a problem in that it has lower adhesive properties to other parts in a module, and thus interlayer peeling may be easily induced when the module is used for a long period of time, which results in degraded efficiency or corrosion caused by moisture penetration. In addition, since the EVA material has lower resistance to UV radiation, it may be easily changed in color or discolored, which also results in degraded efficiency of the module. Further, the EVA material has a problem in that stress generated during a curing process causes damage of elements.
Meanwhile, a fluorescent material may be typically mixed with the encapsulant for LEDs to realize white light in backlight units (BLUs) using the LED or in lightings using the LED, and a photoconversion material may be mixed with an encapsulant of the photoelectric conversion element. However, the fluorescent material or the photoconversion material may precipitate during a curing process of the encapsulant before the encapsulant is sufficiently cured. To solve the above-mentioned problems, a predetermined amount of inorganic particles, for example, silica, may often be added to the encapsulant. Addition of the inorganic particles may result in improved physical properties of the encapsulant such as heat resistance, crack resistance and thermal shock resistance.